have since rectified the issue.
You need to mount the hard disk and the data hard disk in disk utility from recovery mode.
And attach an external SSD.
Creating a backup:
Open terminal in recovery and type ditto "/Volumes/<Macintosh HD>/users/<your username>" "/Volumes/<External Disk>/<a folder name>", replacing <Macintosh HD> & <External Disk> with the names of them in the disk utility, <your username> with the name of your user folder, and <a folder name> with the name of a folder that exists on the external disk. This folder can be created by typing into the terminal:
cd "/Volumes/<external disk>"
mkdir <folder name>
Then you need to type
ditto "/Volumes/<Macintosh HD>/Library/Extensions" "/Volumes/<External Disk>/<another folder name>"
rm -rf "/Volumes/<Macintosh HD>/Library/Extensions"
cd "/Volumes/<Macintosh HD>/Library/"
mkdir Extensions
As by removing (but first backing up) kernal extensions, you can use the Mac again.
You will enter your login password, it will hang for a few moments then proceed to going back to the software update.
Hope this helps everyone!